Drying capacity

Another valuable drying agent of general application is anhydrous calcium sulphate, marketed under the name of Drierite. It is rapid in its action, but has only a limited drying capacity because it forms the hydrate 2CaS04,H20 and thus combines with only 6-6 per cent, of its weight of water. The vapour pressure of the system ... 

As a rough approximation it may be assumed that one mg. of water contained in one litre of gas at 25-30° exerts a 1 mm. partial vapour pressure. Obviously, the lower the residual water content or the vapour pressure, the more intense is the ultimate drying capacity of the substance. 

Fig. 2. Drying capacity of selected drying agents in liquid form. A represents lithium chloride B, calcium chloride C, sulfuric acid D, glycerol E, triethylene...

Direct type, hatch operation Laboratory drying capacities, investment and operating costs are high. Long drying times ments under Pastes and Sludges... 

The critical dimension of a centrifugal-disk chamber is the diameter. Vertical height is usually 0.5 to 1.0 times the diameter the large cone is needed mainly to accelerate to the discharge duct and prevent settling it contributes httle to drying capacity. 

A desiccator is frequently also employed for the thorough drying of solids for analysis and for other purposes. Its efficient operation depends upon the condition of the desiccant the latter should therefore be renewed at frequent intervals, particularly if its drying capacity is low. For dealing with large quantities of solid a vacuum desiccator is advisable. 

Steam washers These spray FW or condensate into the steam to dilute, rinse, and remove entrained contaminants. Additional steam drying capacity is required to deal with the spray water. 

Irrespective of the method used to produce the granules and the consequent batch size, a signiflcant factor in scale-up is the increase in drying capacity in larger equipment. The heat delivered to the bed of fluidizing granules comes from a combination of inlet air temperature and volume, and, to a lesser extent, inlet air dew point. As previously mentioned, the process air volume is also responsible for fluidization behavior, and this will be the first variable to be considered. 

The drying capacity of the air depends upon the relative humidity (RH) of the incoming air. At 100% RH, the air is holding the maximum amount of water possible at a given temperature, but if the temperature of the air is raised, the relative humidity drops and the air can hold more moisture. If air is saturated with water vapor at a given temperature, a drop in temperature will force the air mass to relinquish some of its moisture... 

To fluidize and thus granulate and dry the product, a certain quantity of process air is required. The volume of the air required will vary, based upon the amount of material that needs to be processed. The ratio of drying capacity of the process air and quantity of the product needs to be maintained constant throughout the scaling-up process. However, some suppliers of the equipment provide higher drying capacity for their laboratory unit... 

Choose an inlet air temperature that is high enough to negate weather effects (outside air humidity or inside room conditions). The air temperature should not be detrimental to the product being granulated. (To achieve consistent process year round, a dehumidification/humidification system is necessary, which provides the process air with constant dew point and, hence, constant drying capacity.)... 

The scale-up from the laboratory equipment to production size units is dependent on equipment design which may or may not have been scalable as far as its dimensional feature or components selection is concerned. The importance of scalability is well understood and accepted by the manufacturers of fluid-bed processors. Various sizes in their product line are logically designated and manufactured. Airflow in the fluid-bed process is a critical parameter. The design and selection of the processor is very important for the laboratory and production unit. Because airflow is one of the components of the drying capacity of a fluid-bed system, ratio of air volume per kg or liter of the product is very critical to achieve scale-up that is linear. 

The process of drying while applying spraying solution is a critical unit operation. This mass transfer step was previously discussed. The temperature, humidity, and volume of the process air determines the drying capacity. If the... 

Ratio of granulation spray rate to the drying capacity of the fluidization air volume... 

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